A major focus for this project during the past year has been the protein II family of constituents of gonococcal outer membranes. One or more of these proteins may be present: all are heat modifiable, susceptible to exogenous proteases, and have similar 125I-peptide map patterns. However, at least five different protein(s) II may be found in a single strain of gonococci, and each of the protein II constituents exhibits slightly diffeent properties such as subunit size, dependence on 2-mercaptoethanol and heat for electrophoretic migration characteristics, and correlation with colonial opacity. Variation in pilus subunit molecular weights has aslo been studied using pilus-specific antisera. Many different subunit molecular weight forms of pipi can be found within given strains. These diverse strains also differ from one another in the apparent sizes of their pilus subunit variants. Changes in pilus subunit form do not accompany changes in proein II constitution. Although not absolutely correlated, changes in piliation phenotype (P plus and P plus plus) are usually accompanied by changes in pilus subunit molecular weight.